Line an 8 by 8 inch square baking dish with aluminum foil and set aside.
In a large microwave safe bowl, combine the white chocolate chips and the sweetened condensed milk. Cook at half power for one minute. Stir very well. Continue cooking in 30 second intervals, stirring well between each one, until smooth. Be careful not to overcook. (You will likely only need 2 minutes total - at most.)
Add in the Rum Chata and whisk until smooth. It will be chunky at first, but will smooth out as you whisk swiftly.
Whisk in the vanilla extract and cinnamon.
Pour into the prepared pan. Allow to cool compltely and set for at least four hours. This recipe is easier to cut if you let it chill in the refrigerator.
To cut, remove aluminum foil from hardened fudge. Trim off the edges. Cut in half, then in half again to have four equal squares. Cut each quarter into thirds, one way and then the other. Each quarter will give you 9 pieces, for a total of 36 squares.
Store in an air tight container at room temperature for up to 2 weeks.
I have had good results with this fudge using 1/2 cup of Rum Chata and I know others have as well. Given that many people have had difficulty with it setting at that amount, I'm changing it to 1/4 cup. I want this recipe to work great for everyone.